In recent years, solid state imaging devices have been used for input units of digital cameras, scanners, and the like, and high-speed image readout has been required for such solid state imaging devices. In order to meet the requirement, for Metal-Oxide-Semiconductor (MOS) solid state imaging devices in which pixels are arranged two-dimensionally in rows and columns (hereinafter, a solid state imaging device in which pixels are arranged two-dimensionally in rows and columns is referred to also as a “two-dimensional solid state imaging device”), various methods have been proposed for increasing operating frequency of a scan circuit which generates timings of readout of pixel signals from a common signal line, or for adapting a multi-output structure having a plurality of outputs, for example. Furthermore, for solid state imaging devices which are used in scanners and include line sensors, methods have been proposed for reading out pixel signals from a plurality of the line sensors by delaying respective drive start cycles of the line sensors, for example.
With reference to FIGS. 1 and 2, the following describes the method for reading out pixel signals from a plurality of the line sensors by delaying respective drive start cycles of the line sensors, which is disclosed in Patent Reference 1.
FIG. 1 is a diagram showing wiring in a contact multi-chip image sensor which is the solid state imaging device of the prior art. In this solid state imaging device, wiring on a substrate 304 in which all line sensors 302-1, 302-2, . . . , 302-15 are formed drives each of the line sensors independently, and signals of each line sensor are provided to an output line corresponding to the line sensor. In more detail, start pulses φSP1 to φSP15 for starting operation of the respective line sensors and clock pulses φCLK1 to φCLK15 for driving the respective line sensors are inputted directly to all of the line sensors 302-1, 302-2, . . . , 302-15, respectively, and output terminals on the substrate 304 from which signals of the respective line sensors are outputted exist according to the number of all of the line sensors 302-1, 302-2, . . . , 302-15 and are connected to output terminals of the line sensors, respectively.
FIG. 2 is a timing chart for explaining operation of the contact multi-chip image sensor of the prior art.
The line sensor 302-1 is driven by the start pulse φSP1 and the clock pulse φCLK1, and signals are outputted from the line sensor 302-1 to an output terminal Vout1 at a timing which is set by the start pulse φSP1 and the clock pulse φCLK1. In the same manner, the line sensor 302-2 is driven by the start pulse φSP2 and the clock pulse φCLK2, and signals are outputted from the line sensor 302-2 to an output terminal Vout2 at a timing which is set by the start pulse φSP2 and the clock pulse φCLK2, and the line sensor 302-15 is driven by the start pulse φSP15 and the clock pulse φCLK15, and signals are outputted from the line sensor 302-15 to an output terminal Vout15 at a timing which is set by the start pulse φSP15 and the clock pulse φCLK15. The start pulses φSP1 to φSP15 and the clock pulses φCLK1 to φCLK15 are delayed respectively by a predetermined time period which is shorter than a time period required for reading out signals from a light-receiving element of the corresponding line sensor, so that, to the output terminals Vout1 to Vout15, signals which are delayed respectively by the respective predetermined time periods are outputted as shown in FIG. 2.
The signals of the output terminals Vout1 to Vout15 are combined in a common signal line A0 to An according to respective timings of pulses φSWW1 to φSWW15, and then transmitted to a signal processing circuit at a latter stage. Here, to the common signal line A0 to An, as shown in FIG. 2, signals of the first pixels of the line sensors 302-1, 302-2, . . . , 302-15 are sequentially outputted during the first pixel period, signals of the second pixels of the line sensors 302-1, 302-2, . . . , 302-15 are sequentially outputted during the second pixel period, and signals of the final pixels of the line sensors 302-1, 302-2, . . . , 302-15 are sequentially outputted during a final pixel period.
Patent Reference 1: Japanese Unexamined Patent Application Publication No. 8-242345.